Tributes were paid today to a "passionate" London cycling campaigner believed to have drowned while on holiday with his girlfriend in northern Spain.

Barry Mason, 60, co-ordinator of Southwark Cyclists and manager of Surrey Docks City Farm, died while swimming in the sea off Rodiles surfing beach in Asturias. It is thought he may have suffered a heart attack.

An emergency helicopter went to the scene on Thursday last week but a doctor was unable to revive father-of-two Mr Mason, who had a long-term partner, Cheryl.

Events he organised included mass Christmas Day cycling in central London and overnight bike rides on the shortest night of the year. He also helped to set up Bermondsey and Rotherhithe Green Enthusiasts, bringing together a variety of environmental organisations.

Colleagues say he constantly monitored planning applications across Southwark to ensure they had enough cycle parking and other bike-friendly measures. Southwark Cyclists secretary Colin Hartridge-Price said: "Barry was visionary and energetic over very many years in campaigning to improve safety and security for cyclists, particularly in the Southwark area.

"He also helped many cyclists gain confidence and skill through the numerous cycle rides he led and his cycle maintenance classes."

One cyclist's website tribute read: "His energy and enthusiasm were off the scale. Hardly anyone could be as passionate and as dedicated as Barry was. He was the heart of the community, an incredible organiser and project manager, and his immense charm and tenacity made him a fantastic campaigner."

Police in Spain are awaiting post-mortem examination results, said a spokesman.